SHR-1681

SHR-1681 is a selective small molecule inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6), developed by Jiangsu Hengrui Pharmaceuticals and its subsidiary Suzhou Suncadia Biopharmaceutical. Unlike the majority of CDK4/6 inhibitors currently on the market or in development, which are administered orally (such as palbociclib or Hengrui's own dalpiciclib), SHR-1681 is an injectable formulation designed for intravenous administration. The drug is intended to treat advanced malignant solid tumors by inhibiting the CDK4/6-cyclin D complex, which prevents the phosphorylation of the retinoblastoma (Rb) protein. This inhibition leads to cell cycle arrest in the G1 phase, thereby suppressing tumor cell proliferation. SHR-1681 is currently being evaluated in Phase I/II clinical trials to determine its safety, pharmacokinetics, and preliminary efficacy in patients with various advanced solid malignancies.